A microelectromechanical system (MEMS) is a microdevice that integrates mechanical and electrical elements on a common substrate using microfabrication technology. The electrical elements are typically formed using known integrated circuit fabrication techniques. The mechanical elements are typically fabricated using lithographic and other related processes to perform micromachining, wherein portions of a substrate (e.g., silicon wafer) are selectively etched away or added to with new materials and structural layers. MEMS devices include actuators, sensors, switches, accelerometers, and modulators.
MEMS switches (i.e., contacts, relays, shunts, etc.) have intrinsic advantages over their conventional solid-state counterparts (e.g., field-effect transistor (FET) switches), including superior power efficiency, low insertion loss and excellent isolation. However, MEMS switches are generally much slower than solid-state switches. This limitation precludes applying MEMS switches in certain technologies, such as wireless communications, where sub-microsecond switching is required.
MEMS switches typically include a suspended connecting member called a “beam” that is electrostatically deflected by activating an actuation electrode. The deflected beam touches one or more electrical contacts, thereby establishing an electrical connection between the contacts. When the beam is anchored to one contact while being suspended over another other in cantilever fashion, it is called a “cantilevered beam.” When the beam is anchored to the substrate at opposite ends and is suspended over one or more electrical contacts, it is called a “bridge beam.”
The key feature of a MEMS switch that dictates its switching speed is the form of the beam. In particular, the highest switching speed is defined by the resonance frequency of the beam, which is a function of the beam geometry. Conventional beams in MEMS switches have essentially a solid rectangular structure. While such a structure is relatively easy to fabricate, is strong, and is suitable for many switching applications, the resonance frequency of the beam is generally too low to perform high-speed switching.
In the Figures, like reference numbers refer to like elements.